页岩油藏渗吸驱油剂体系性能评价

Performance evaluation of a system of imbibition oil displacement agent in shale reservoir

由于页岩油藏的超低渗透率和复杂的孔隙结构,从页岩油储层中采油仍然是一个重大挑战。表面活性剂作为一种潜在的解决方案,通过降低界面张力和改变润湿性来提高非常规油藏的原油采收率。本研究旨在通过研究页岩油储层的自发渗吸行为,评价表面活性剂在页岩油藏中的应用潜力。结果表明,复配渗吸驱油体系0.15 wt%CA-90+0.15 wt%SDS,在地层条件下界面张力降低至1.03×10^(-2)mN/m;亲油岩心片润湿接触角降低了86°,岩石润湿性由油湿转变为水湿,毛管力由油渗吸驱油阻力转变为渗吸驱油动力;在含水率为70%时,乳状液黏度降低至23.4 mPa·s,其黏度接近原油黏度,但流动性更强,更有利于提高采收率;0.15 wt%CA-90和0.15 wt%SDS的动态吸附量分别为0.85和0.97 mg/g,具有较好的抗吸附能力,对页岩渗透率伤害率低于8%;滑溜水+复配体系的渗吸采收率可以达到31.27%,相比滑溜水体系中自发渗吸采收率(19.43%)提高了11.84%,渗吸驱油效率提高了60.94%,极大地提高了页岩油藏的采收率。

The recovery of crude oil from shale oil reservoirs remains a significant challenge due to the ultra-low permeability and complex pore structures.Surfactants have been increasingly investigated as a potential method to enhance oil recovery in unconventional reservoirs by reducing interfacial tension and altering wettability.In this work,the performance of surfactants for potential application in shale oil reservoirs was evaluated by investigating spontaneous imbibition behavior.The results showed that the interfacial tension of 0.15 wt%CA-90+0.15 wt%SDS was reduced to 1.03×10^(-2) mN/m under formation conditions.The wetting contact angle of the oil-wet core sheet was reduced from 135.5°to 49.5°,i.e.,the wettability of the rock was changed from oil-wet to waterwet,and the capillary force was thus changed from resistance for oil imbibition to driving force.When the water content was 70%,the viscosity of the emulsion decreased to 23.4 mPa·s which was close to the viscosity of crude oil,but the fluidity was higher,which was more conducive to improving oil recovery.The dynamic adsorption capacities of 0.15 wt%CA-90 and 0.15 wt%SDS were 0.85 mg/g and 0.97 mg/g,respectively,which had good anti-adsorption ability,and the damage rate of shale permeability was less than 8%.The imbibition recovery of slick water+compounded system could reach 31.27%,which was much higher than that of spontaneous imbibition recovery in slick water system(19.43%),and the imbibition oil displacement efficiency was thus increased by 60.94%,which greatly improved the oil recovery for shale reservoirs.